Electric switch



Oct. 17, 19$? c. w. UPTON, JR 3,348@@2 ELECTRIC SWITCH Filed Sept. 24, 1965 2 sheets-sham.v 1

INVENTOR Ches ier W. Upton):

MJWO/AQL ATTORNEY Oct. 17, 1967 c w. UPTON, JR

ELECTRIC SWITCH 2 Sheets$heet 2 Filed Sept. 24, 1965 FIG. 2

ALLA

FIG. 3

I68 I [64A United States Patent 3,348,002 ELECTRIC SWITCH Chester W. Upton, Jim, lenn Township, Traiford, Pa,

assignor to Westinghouse Electric Corporation, Pittsburgh, Pa, a corporation of Pennsylvania Filed Sept. 24, 1965, Ser. No. 489,972 9 Claims. (Cl. 20048) ABSTRACT OF THE DISCLQSURE This invention relates generally to electric switches and more particularly to switches suitable for use as grounding switches. The switch blade of an electric switch is pivotally mounted on a rotatable shaft and is actuated to engage and disengage a relatively stationary contact. An arcing contact is disposed adjacent to and spaced from the stationary contact and is electrically connected directly to the stationary contact by an electrically conducting means with the arcing contact being nearer to the free end of the blade at a predetermined position during the rotation of the blade toward the stationary contact than the stationary contact. The blade may be actuated to engage the stationary contact. The blade may be actuated to engage the stationary contact by a stored energy means by releasing a latch to permit the stored energy means to actuate a plunger which applies an impulse of force to the blade at substantially its center of percussion.

In electric power systems, automatic grounding switches are sometimes utilized to protect transformers which are located remotely from a high voltage circuit breaker that controls the power circuit which supplies the transformers. If an interna fault occurs in the transformer, the grounding switch is actuatd by suitable control devices to deliberately ground the power circuit on the high voltage side of the transformer to thereby actuate protective relays at the remote circuit breaker to trip the breaker. It has been found that conventional high speed grounding switches of the swinging blade type are limited in their ability to close against extremely high currents of more than 10,000 amperes at higher transmission voltages because of the magnetic repulsive forces associated with the current loop which is established during the closing operation of the grounding switch. This current loop is completed as a prestrike are between the free end of the switch blade and the associated stationary contact of a conventional grounding switch which is initiated as the switch blade approaches a closed position with respect to the associated stationary contact. A typical approach to this problem is to arrange the tip or free end of the swinging blade to engage the associated stationary contact at substantially a right angle with the result that the magnetic repulsive forces occurring during the prestrike are are applied to the swinging blade substantially or effectively tangentially. As the voltage and current ratings required for high speed grounding switches increase, the mechanical resistance to complete closing of the swinging blade due to the magnetic repulsive forces is extremely high and the swinging blade tends to be blown back to the open position rather than to close and maintain the desired ground on the power system or circuit which is necessary to protect an associated electrical apparatus, such as a transformer. The magnitudes of the magnetic repulsion forces experienced in conventional electric switches of the swinging blade type are discussed in detail in the book, Electrical Coils and Conductors, by Herbert B. Dwight, 1st ed., New York, McGraw-Hill, 194-5, pp. 335344. In addition, a problem arises in providing suitable grounding switches as the voltage ratings and corresponding sizes increase due to the increased operating forces required to actuate such grounding or other types of switches and to minimize the problems of stopping and preventing rebound for a blade accelerated at extremely high speeds in order to close against currents of high magnitudes, such as 10,000 amperes or more. it is therefore desirable to provide improved electric switches which are particularly suitable for use as high speed grounding switches capable of closing against extremely high currents at relatively high transmission voltages, to reduce the operating forces required to actuate such grounding switches or other types of electric switches and to minimize both accelerating and decelerating forces.

It is an object of this invention to provide a new and improved high speed electric switch.

A more specific object of this invention is to provide an improved means for insuring the closing of a switch while extremely high currents are flowing through the switch.

A further object of the invention is to provide an improved means for employing the magnetic forces which result during the closing of a switch of the swinging blade type to assist in the closing of the switch.

Another object of this invention is to provide an improved operating mechanism for an electric switch.

A further object of this invention is to provide an improved means for reducing the forces involved in accelcrating and decelerating the blade of a switch of the swinging blade type.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a view, in side elevation, of a grounding switch embodying the principal features of the invention with the switch shown in the open position;

FIG. 2 is a view, in side elevation, of a grounding switch illustrating a second embodiment of the invention with the switch shown in the open position;

FIG. 3 is an enlarged view, in side elevation, of the actuating mechanism for the switch shown in FIG. 2, the mechanism being shown in a position corresponding to the open position of the switch;

FIG. 4 is a view, similar to FIG. 3, showing the actuating mechanism in a position corresponding to the closed position of the switch shown in FIG. 2; and

FIG. 5 is an enlarged view, in end elevation, of a portion of the actuating mechanism for the switch shown in FIG. 2, illustrating a latch means which may be employed with the switch shown in FIG. 2 when the switch is in the open position.

Referring now to the drawings and FIG. 1 in particular, the structure shown comprises a grounding switch 10 which is of the type described in greater detail in US. Patent 2,757,255 which issued July 31, 1956, to I. B. Owens et al. and which is assigned to the same assignee as the present application. The grounding switch 10 comprises a switch blade 20 which is disposed to engage a main stationary contact member 22 supported by an insulator stack 24 which in turn is mounted upon a base 46. A generally U-shaped corona shield 62 may be attached for extra high voltage applications to a mounting plate 63 which is disposed on top of the insulator stack 24 adjacent to the stationary contact member 22. The base 46 may be supported in turn by a suitable structural framework (not shown). As illustrated, the switch blade 20 may be utilized for grounding a power circuit or transmission line when actuated by an operating mechanism 30 to a closed position with respect to the associated stationary contact member 22. The blade 20 is normally retained in the open position, as shown by the full lines :3 in FIG. 1, and it may be so mounted that it travels or rotates approximately 75 degrees between the open and closed positions with respect to the associated stationary contact member 22.

As explained in detail in the above-mentioned patent, the blade 20 is normally retained in the open position and is biased to the closed position by a spring assembly or other suitable energy storing means (not shown). When the blade 20 is actuated to the closed position by the operating mechanism 30, the blade 20 is then retained in the closed position and the operating mechanism 30 may be reset and the blade 20 actuated to the open position by a resetting mechanism which is enclosed in a housing 31 which is mounted upon the base 46. The resetting mechanism may be manually operated by a handle 32 which is pivotally connected to a vertical shaft 36 rotatably mounted in the bearing supports 34 and 33 which may be attached in turn to the framework which supports the base 46. The shaft 36 is connected to one end of a horizontally disposed rod 44 through a crank arm 42. The other end of the rod 44 is connected or coupled to a rotatable sleeve 48 through a lever arm 52 which is part of the operating mechanism for the switch 10.

As shown by the dot-dash lines in FIG. 1, the handle 32 may be raised to a substantially horizontal position when it is desired to operate the resetting mechanism. The handle 32 is utilized to rotate the vertical shaft 36 thereby operating the resetting mechanism as described in detail in the above-mentioned patent. The handle 32 may be locked in the position shown by the full lines in FIG. 1 by means of a padlock (not shown).

As described in detail in the above-mentioned patent, the switch blade 20 of the grounding switch is actuated by an operating mechanism that comprises a rotatable shaft 49 having a lever arm (not shown) secured thereto. The lever arm is connected to a spring assembly (not shown) which is compressed when the blade is in the open position and is held under compression by a primary latch (not shown) carried by an arm (not shown) secured to a sleeve 48 which is disposed in a coaxial relation with the shaft 49 for the blade 20. The primary latch is released by a lever (not shown) which is actuated by a tripping solenoid (not shown) and the spring assembly rotates the shaft 49 to close the switch blade 20. A secondary latch (no-t shown) engages the lever on the shaft 49 to prevent rebound upon closing and to hold the switch blade 20 in a closed position. The operating mechanism is reset by rotating the sleeve 48 and the primary latch arm in one direction to cause the associated secondary latch to be disengaged from and the primary latch engaged to the shaft lever and the spring assembly. The sleeve 48 is then rotated in the opposite direction to open the switch blade 20 and to compress the closing spring assembly.

In the operation of the grounding switch 10, when the tripping solenoid included in the operating mechanism 30 is energized, a lever is actuated to cause a primary latch to release a spring assembly which rotates the shaft 49 through a lever arm to thereby rotate the switch blade 20 in an arcuate path in a counterclockwise direction about the shaft 49 to a closed position in which the free end or tip of the switch blade 20 engages the main stationary contact member 22. As described in detail in the abovementioned patent, when the primary latch of the operating mechanism 36 is released by the associated tripping solenoid, the spring assembly provided is free to rotate the switch blade 20 from the open position shown in FIG. 1 to the closed position shown in phantom with the resetting mechanism previously described being eifectively or operatively uncoupled from the operating mechanism 30.

It is to be noted that during a closing operation of the grounding switch 10, as the free end or tip of the switch blade 20 approaches a closed position with respect to the stationary contact member 22, a prestrike arc is initiated between the free end of the switch blade 20 and the stationary contact 22. The distance between the stationary contact member 22 and the free end of the switch blade 20 at the time that the prestrike arc is initiated depends upon the potential or voltage difference between the stationary contact member 22 and ground or zero potential. In the absence of the auxiliary contact assembly which will be described hereinafter, a current loop would result due to the prestrike arc between the stationary contact member 22 and the free end of the switch blade 20 which is generally a right angle in configuration with the apex of the right angle pointing gene-rally away from the stationary contact member 22. The repulsive magnetic forces produced by such a current loop in the absence of the auxiliary contact assembly 70 would tend to resist the closing of the switch blade 20 against extremely high currents and would tend to blow the switch blade 26 back to the open position, as shown in FIG. 1, rather than permitting the switch blade 20 to reach the closed position shown in phantom in FIG. 1.

In accordance with the disclosed invention, the auxiliary contact assembly 70 is disposed adjacent to the main stationary contact member 22 and is supported at the top of the insulator stack 24. The auxiliary contact assembly 70 includes an auxiliary arcing contact 74 that is disposed adjacent to and spaced from the main stationary contact member 22 and is also spaced from the arcuate path of the switch blade 20. The arcing contact 74 is mounted on a supporting member 72 which in turn is supported on top of the insulator stack 24 and is formed from an electrically conducting material, such as copper, to electrically connect the auxiliary arcing contact 74 to the main stationary contact member 22. It is to be noted that the arcing contact 74 is radially spaced from the arcuate path of the switch blade 20 at a predetermined position of the switch blade 20 in which the longitudinal dimension of the switch blade 20 lines up with a line extending between the arcing contact 74 and the shaft 49 about which the switch blade 20 rotates, as indicated generally at 23. It is also to be noted that just before the switch blade 20 reaches an aligned position with respect to the arcing contact 74, as indicated at 23, the arcing contact 74 is disposed relatively closer to the free end or tip of the switch blade 20 than the main stationary contact member 22. In other words, when the switch blade 20 reaches a position just to the right of the aligned position, as indicated at 23, and spaced therefrom as indicated by the small distance B, in a clockwise direction from the aligned position, the distance between the free end of the switch blade 20 and the arcing contact 74 will be relatively less than the distance between the free end of the switch blade 20 and the main stationary contact member 22 to insure the prestrike are, as indicated at 21, will be initiated between the free end of the switch blade 20 and the arcing contact 74 before a prestrike arc occurs between the free end of the switch blade 20 and the main stationary contact member 22.

Considering the operation of the grounding switch 10 as modified by the auxiliary contact assembly '70, during a closing operation, the switch blade 20 will be actuated in a counterclockwise direction about the shaft 49 by the operating mechanism 30 until the switch blade 20 reaches the position just to the right of the aligned position indicated at 23 and spaced from the aligned position, as indicated at B. A prestrike arc will then be initiated as indicated at 21 before any prestrike arc occurs between the free end of the switch blade 24} and the main stationary contact member 22. The current flow through the switch blade 20 and the prestrike arc 21 will form a current loop which is generally an obtuse angle in configuration with the apex of the obtuse angle pointing generally away from the main stationary contact member 22 until the switch blade 20 reaches an aligned position with the arcing contact 74, as indicated at 23. While the switch blade 20 rotates through the zone of travel indicated at B, a component of the magnetic forces produced by the above-described current loop will tend to oppose the rotation of the switch blade 20 in a counterclockwise direction about the shaft 49 toward the main stationary contact 22, but the inertia imparted to the switch blade 20 by the operating mechanism 30 will be sufiicient to carry the switch blade 20 through the small zone of resistance to the rotation or travel of the switch blade 20 until the blade 20 reaches and passes an aligned position with respect to the arcing contact 74, as indiciated at 23. It is to be noted that once a prestrike arc is initiated between the free end of the blade 20 and the arcing contact 74, the prestrike arc will tend to continue between the free end of the blade 20 and the arcing contact 74 until the blade 20 reaches a position which is relatively close to the main stationary contact member 22. As the blade 20 passes the aligned position with respect to the arcing contact 74 as indicated at 23, the prestrike arc between the free end of the blade 20 and the arcing contact 74 as indicated at 21' will form a current loop which is generally an obtuse angle in configuration with the apex of the angle pointing generally toward the main stationary contact member 22. The magnetic forces produced by a current loop of the latter configuration will act to push or actuate the blade 20 in a counterclockwise direction toward the main stationary contact member 22 until the blade 2% approaches final engagement with the stationary contact member 22. The prestrike are 21' may possibly transfer to the main stationary contact member 22 just before the blade 20 reaches the main stationary contact member 22 to produce a current loop and associated slight magnetic repulsive forces which tend to oppose the final travel of the blade 20 just before the blade 2%) reaches an engaged or closed position with respect to the stationary contact member 22. The blow off forces that would otherwise be present in a conventional switch structure are substantially reduced of eliminated and the blade 20 is actually assisted in its movement to a final engaged position during all or almost all of the final portion of its travel or rotation toward the stationary contact member 22.

It is to be noted that the relative spacings between the main stationary contact member and between the arcing contact 74 and the arcuate path of the blade 20 depend upon the operating voltage existing between the stationary contact member 22 and ground or zero potential in a particular application. The small zone of resistance to rotation of the blade 20 just before the blade 20 reaches an aligned position with respect to the arcing contact 74 may be minimized by arranging the prestrike arc to be initiated between the arcing contact 74 and the free end of the blade 20 just before the blade 20 reaches an aligned position with respect to the arcing contact 74. It is also to be noted that the prestrike arc between the free end of the blade 20 and the arcing contact 74 is substantially in line with the axis of the blade 20 when the prestrike arc is initiated rather than being disposed at substantially a right angle with respect to the axis of the switch blade as in a conventional switch structure.

After the grounding switch 20 has ben automatically closed by the operating mechanism as described in detail in the patent previously mentioned, the sleeve 48 is first rotated in a counterclockwise direction by the resetting mechanism previously described to reset the op erating mechanism 30 and is then rotated in a clockwise direction to open the blade 20 and also compress the spring assembly which forms part of the operating mechanism 30.

Referring now to FIG. 2, there is shown a grounding switch 100 which in general is similar to the grounding switch previously described except that the grounding switch 10% includes an operating mechanism 130 that applies an actuating force to the switch blade 120 of the grounding switch 10% substantially at the center of percussion of the switch blade 120. Similarly to the grounding switch 10, the grounding switch 100' comprises a blade 120 which is rotatably supported on an operating shaft 49 to engage a main stationary contact member 122 supported on an insulator stack 24 which in turn is mounted upon a base 46. The operating shaft 4? is rotatably supported by a suitable bearing bracket 199 which in turn is supported on the base 46. The base 46 may be supported by suitable structural framework (not shown). A generally U-shaped corona shield 62 for high voltage applications may be disposed adjacent to the stationary contact member 122 and supported on a mounting plate 63 on top of the insulator stack 24. The grounding switch also includes an auxiliary contact assembly 70 which is identical to the auxiliary contact assembly 70 previously described in connection with the grounding switch 10 and which is provided for the same purpose.

The switch blade is normally retained in the open position by a latch assembly 210 or other releasable device which will be described hereinafter and is biased to the closed position by a spring assembly or other suitable energy storing means which will be described more fully hereinafter. The blade 120 may be retained in the closed position by a suitable latching means (not shown) which may be manually or electrically released and may be manually reset by a hookstick (not shown) which may engage a resetting hookeye 198 provided at the free end of the blade 124) to rotate the blade 120 from the closed position shown in FIG. 2 in phantom to the open position shown in FIG. 2 in solid line or vice-versa during certain operating condtions.

As shown in FIGS. 3 and 4, the operating mechanism 13!) for the grounding switch 10% comprises an actuating plunger or rod 164 which is normally disposed inside an upper housing portion 175 and a lower housing portion 152 when the blade 120 is in the open position, as shown in FIG. 2. As shown in FIGS. 2. and 3, the actuating rod 164 is disposed adjacent to the blade 12%) at substantially a right angle with respect to the switch blade 120 when the blade 120 is in the open position to apply an impulse of force to the blade 120 when the actuating rod 164 is released substantially at the center of percussion of the blade 120 to thereby actuate the blade 120 toward a closed position with respect to the stationary contact member 122. It is to be noted that the center of percussion of the blade 12% which is similar to a homogeneous rod in configuration is located at a point which is spaced from the shaft 49 substantially twothirds the distance between the axis of rotation of the blade 12th at the shaft 49 and the free end of the blade 120. An important advantage of applying the actuating force to the blade 120 at substantially the center of percussion is that the force required to actuate the blade 120 into a closed position with respect to the stationary contact member 122 is minimized. In addition, the forces at the bearings of the shaft 49 are also minimized by applying the actuating force to the blade 120 at substantially the center of percussion.

As best shown in FIGS. 3 and 4, the actuating rod 164 is slidably disposed for reciprocating motion within a tubular guide member 174 which is disposed inside the upper housing portion 175. The upper and lower guide bearings 172 and 173, respectively, are provided at the ends of and supported by the tubular guide member 174, as shown in FIGS. 3 and 4. In order to prevent the entrance of moisture or ice inside the upper housing portion 175 when the operating mechanism 136) is in the normal position shown in FIG. 3, a cup-shaped hood member 162 is secured to the top of the actuating rod 164 and includes an overhanging lip portion 162A to insure that any ice which forms on the hood member 162 will extend from the lip portion A to the top of the lower housing portion 152. The latter arrangement facilitates the breaking loose of any ice formations which may result and which might otherwise inhibit or slow down the operation of the grounding switch 100. In order to limit the upward travel of the actuating rod 164, as will be explained hereinafter, the lower end of 7 the actuating rod 164 includes an enlarged stop portion 164A which engages the underside of the top of the lower housing portion 152, as shown in FIG. 4, when the actuating rod 164 moves in an upward direction.

In order to actuate the rod 164 and in turn the grounding switch 180 to the closed position, a coil spring assembly 176 is disposed in the annular space between the upper housing portion 175 and the tubular guide member 174 when the switch 108 is in the open position. The hood member 162 at the upper end of the actuating rod 164 acts as an upper spring seat for the spring assembly 176 while the top of the lower housing portion 152 inside the upper housing portion 175 acts as lower spring seat for the spring assembly 176.

In order to retain the spring assembly 176 in a compressed or loaded condition as shown in FIG. 3, a primary latch member 184 is pivotally mounted inside the lower housing portion 152 on the pivot pin 166 which in turn may be supported at the ends by brackets or other means provided on the wall portions of the lower housing portion 152. The primary latch member 184 is generally L-shapedin configuration and includes a shoulder portion 167 at the lower end of one leg portion which normally engages a needle bearing roller pivotally mounted at the lower end of the actuating rod 164 when the blade 120 is in the open position, as shown in FIG. 2. In order to maintain the primary latch member 184 in an engaged relation with the lower end of the actuating rod 164 as shown in FIG. 3, the biasing spring 182 is disposed between the top of the lower housing portion 152 and the right-hand portion of the primary latch member 184 to bias the primary latch member 184 in a clockwise direction about the pivot pin 166. In order to limit the clockwise rotation of the primary latch member 184 under the influence of the primary latch member 182 during certain operating conditions of the operating mechanism 130, the stop pin 192 is disposed adjacent the underside of the right-hand portion of the primary latch member 184 opposite the biasing spring 182. It is to be noted that when the spring assembly 176 is compressed as sh wn in FIG. 3, the spring assembly 176 is disposed to actuate the rod 164 and in turn the blade 120 from an open to a closed position with respect to the associated stationary contact member 122 but is normally prevented from closing the blade 120 by the primary latch member 184, as shown in FIG. 3.

In order to disengage the primary latch member 184 from the lower end of the actuating rod 164 and to release the spring assembly 176, a remotely controlled device, such as the core or armature 194 of a solenoid 190 having a coil 191 may be disposed inside the lower housing portion and mounted on a bracket (not shown) which is attached to one of the side wall portions of the lower housing portion 152. The solenoid coil 191 may be energized through the contacts of a diiferential relay or other protective device (not shown) which is located remotely from the operating mechanism 130 in order to protect an electrical apparatus, such as a transformer. When the coil 191 is energized, the core or plunger 194 is actuated to engage the right-hand end of the primary latch member 184 which is then rotated in a counterclockwise direction about the pivot pin 166 against the biasing force of the spring 182 and against the biasing force of the spring assembly 176 through the actuating rod 164 until the primary latch member 184 is disengaged from the lower end of the actuating rod 164. The actuating rod 164 is then accelerated or actuated rapidly in an upward direction by the spring assembly 176 until the rod 164 reaches the position shown in FIG. 4 in which the stop portion 164A engages the underside of the top of the lower housing portion 152 to thereby apply an impulse of force substantially at the center of percussion of the switch blade 120. The blade 128 is then actuated in a counterclockwise direction about the shaft 49 under the influence of the inertia imparted to the blade 120 by the operating mechanism 138. As explained previously, the blade 128' will move in a counterclockwise direction until just before the blade reaches a position in which the axis of the blade is aligned, as indicated generally at 23. After the blade 120 passes through a small zone of resistance to the closing movement of the switch blade 120 as previously explained, and moves past the in line position with the arcing contact 74, the magnetic forces produced by the current loop will then push or assist the blade 120 toward the final closed or engaged position of the blade 120 with respect to the stationary contact member 122. As previously explained in connection with the grounding switch 10, a small zone of resistance may be experienced by the blade 126 when the prestrike are transfers from the arcing contact 74 to the stationary contact member 122 just before the blade 128 reaches a final engaged position with respect to the stationary contact member 122.

Since the operating mechanism 130 is not directly connected or coupled to the switch blade 120, a secondary latch means 210 may be provided to retain the switch blade 120 in an open position as shown in FIG. 2 in order to prevent any movement of the blade 120 under the influence of strong winds which might cause movement of the blade 120 from the normal open position as shown in FIG. 2. As shown in FIG. 5, the secondary latch means 210 comprises a latch member 220 which is pivotally mounted on a pivot pin 212 which in turn is supported on a suitable structural framework (not shown) along the length of the switch blade 120 when the blade 120 is in the open position. The latch member 220 includes a hook portion 222 which normally engages the switch blade 102 when the blade 120 is in the open position shown in FIG. 2. In order to facilitate the releasing of the secondary latch means 210 when the actuating rod 164 is actuated in an upward direction by the spring assembly 176, the latch member 221) may be biased in a clockwise direction about the pivot pin 212 by a relatively light biasing spring such as a torque spring disposed on the pivot pin 212 to engage the latch member 220. In order to actuate the latch member 220 to an engaged position with respect to the blade 120 when the actuating rod 164 is reset to its normal position shown in FIG. 3, the latch member 220 may also include a projecing lug porion 224 which is engaged by the hood member 162 of the operating mechanism 130 to rotate the latch member 220 in a counterclockwise direction about the pivot pin212 as the actuating rod 164 moves in a downward direction during a resetting of the operating mechanism 130 as indicated in FIG. 5.

In order to reset the operating mechanism 130 and to return the switch blade 120 to its normal open position after an automatic closing operation, the resetting hookeye 198 may be actuated by a hookstick (not shown) to rotate the blade 121 in a clockwise direction from the closed position shown in phantom to the open position shown in FIG. 2 while at the same time compressing the spring assembly 176 to the position shown in FIG. 3'. It is to be noted that as the actuating rod 164 is actuated in a downward direction the roller 168 will ride down the cam surface 184A provided on the left-hand portion of the primary latch member 184 until the roller engages or is captured by the shoulder portion 167 provided on the primary latch member 184.

It is to be noted that the operating mechanism 130 as disclosed is uniquely adapted to cooperate with the auxiliary contact assembly 70 provided with the grounding switch 188 since the operating mechanism 1311 need only impart sufficient inertia to the switch blade 100 to carry the switch blade through the small zone of resistance, as indicated at B, during closing rotation of the switch blade which occurs just prior to the position of the switch blade in which the switch blade is sub stantially aligned with a line extending from the shaft 49 to the arcing contact 74. As previously explained once the blade passes the latter operating position during its rotational travel, the magnetic forces produced by the shape of the current loop which is then generated will 9 assist the final closing movement of the switch blade 120 to an engaged position with respect to the stationary contact member 122. It is to be understood that in certain applications a latching means may be provided to retain the switch blade 12% of the grounding switch 100 in a closed position and that such a latching means may be manually operated to free the switch blade 120 to be actuated back to the normal open position by the resetting hookeye 198 when desired.

It is to be understood that the teachings of the invention may be applied to electric switches other than grounding switches in order to facilitate the closing of a switch blade of the swinging blade type against extremely high currents or to minimize the mechanical forces required to actuate the blade between the different operating positions. It is also to be understood that the teachings of the invention may be applied either to a single pole switch or to a three phase or polyphase switch which may be actuated by a common operating mechanism by extending the operating shaft 49 of the grounding switch or by providing a common operating member which is actuated by a single operating mechanism, such as the operating mechanism 130 of the grounding switch 100.

The apparatus embodying the teachings of this invention has several advantages. For example, the auxiliary contact assembly as provided permits the closing of an electric switch particularly of the grounding switch type against extremely high currents which would otherwise hinder or prevent complete closing of the switch blade under certain operating conditions. More specifically, the magnetic repulsive forces which would otherwise exist in a conventional switch structure are actually employed to assist the final closing movement of the swinging blade rather than opposing the closing movement to an engaged position with respect to the associated stationary contact member. In addition, an operating mechanism is disclosed which minimizes the mechanical forces required to actuate an electric switch, particularly of the grounding switch type, and to decelerate the switch during closing. By applying the actuating force to a switch blade substantially at the center of percussion, the mechanical forces present at the bearings provided at the axis of rotation of the swinging blade are also minimized.

Since numerous changes may be made in the abovedescribed apparatus, different embodiments of the invention may be made without departing from the spirit and scope thereof it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A switch comprising a stationary contact, a rotatable shaft, a switch blade secured to the shaft and rotatable with the shaft in an arcuate path lying in substantially a predetermined plane to actuate the free end of the blade into and out of engagement with the stationary contact, an arcing contact at the same potential as the stationary contact electrically connected directly to the stationary contact by an electrically conducting means and disposed adjacent to and spaced from the stationary contact, the arcing contact being disposed relatively nearer to the free end of the blade than the stationary contact at a predetermined position of the blade during the rotation of the blade toward the stationary contact which is spaced from the stationary contact.

2. A switch comprising a stationary contact, a. rotatable shaft, a switch blade secured to the shaft and rotatable with the shaft in an arcuate path lying in substantially a predetermined plane to actuate the free end of the blade into and out of engagement with the stationary contact, an arcing contact at the same potential as the stationary contact electrically connected directly to the stationary cont-act by an electrically conducting means and disposed adjacent to and spaced from the stationary contact, the arcing contact being spaced from the arcuate path of the blade and disposed relatively closer to the free end of the blade than the stationary contact when the blade reaches a position in its rotation toward the stationary contact in which the arcing contact is substantially in line with the blade to initiate arcing between the arcing contact and the free end of the blade before arcing occurs between the stationary contact and the blade with the arcing between the arcing contact and the free end of the blade forming with the blade an obtuse angle whose apex points generally toward the stationary contact during the final portion of the rotation of the blade into engagement with the stationary contact.

3. A switch comprising a stationary contact, a rotatable shaft, a switch blade secured to the shaft and m-ovable in an arcuate path as the shaft is rotated to actuate the free end of the blade toward and away from engagement with the stationary contact, an arcing contact at the same potential as the stationary contact electrically connected directly to the stationary contact by an electrically conducting means and disposed adjacent to the stationary contact and spaced from the arcuate path of the blade, the arcing contact being disposed relatively closer to the free end of the blade than the stationary contact when the blade is actuated by the shaft toward the stationary contact to a predetermined position in which the arcing contact is substantially aligned with the blade to initiate arcing between the arcing contact and the free end of the blade before arcing occurs between the free end of the blade and the stationary contact.

4. A switch comprising a stationary contact, a rotatable shaft, a switch blade secured to the shaft and movable in an arcuate path as the shaft is rotated to actuate the free end of the blade toward and away from engagement with the stationary contact, an arcing contact at the same potential as the stationary contact electricall connected directly to the stationary contact by an electric-ally conducting means and disposed adjacent to the stationary contact and spaced from the arcuate path of the blade, the arcing contact being disposed relatively closer to the free end of the blade than the stationary contact when the blade is actuated by the shaft toward the stationary contact to a predetermined position in which the arcing contact is substantially aligned with the blade to initiate arcing between the arcing contact and the free end of the blade before arcing occurs between the free end of the blade and the stationary contact with the arcing between the arcing contact and the free end of the blade during the final portion of the rotation of the blade into engagement with the stationary contact forming with the blade an obtuse angle whose apex points generally toward the stationary contact to thereby produce magnetic forces tending to actuate the blade into engagement with the stationary contact.

5. A switch comprising a stationary contact, a rotatable shaft, a switch blade mounted on the shaft and movable with the shaft in an arcuate path between closed and open position into and out of engagement with the stationary contact, and releasable stored energy means disposed a-dja-cent to the blade for applying an impulse of force to the blade transversely substantially at the center of percussion to actuate the blade toward the stationary contact, said stored energy means being disengaged from the blade when the blade is in closed position.

6. A switch comprising a stationary contact, a rotatable shaft, a switch blade mounted on the shaft and movable with the shaft in an arcuate path into and out of engagement with the stationary contact, stored energy means disposed adjacent to the blade for applying an impulse of force to the blade substantially at the center of percussion to actuate the blade toward the stationary contact, and an arcing contact electrically connected to and spaced angularly from the station-ary contact with respect to the aru'ate path of the blade, the arcing contact being spaced from the arcuate path of the blade and 1 1 disposed relatively closer to the free end of the blad than the stationary contact when the blade reaches a position in its movement toward the stationary contact in which the arcing contact is substantially in line with the blade.

7. A switch comprising a stationary contact, a rotatable shaft, a switch blade secured to the shaft and mov able in an arcuate path with the shaft between open and closed positions with respect to the stationary contact, an actuating plunger dis-posed adjacent to the blade in the open position to engage the blade transversely substantially at the center of percussion, stored energy means disposed adjacent to the plunger to apply an impulse of force to move the plunger toward the blade, a latch disposed to maintain the stored energy means in a stored energy condition, and controllable means for actuating the latch to release the stored energy means and to actuate the plunger to rotate the blade toward the closed position the plunger being disengaged from the blade when the blade is in the closed position.

8. A switch comprising a stationary contact, a rotatable shaft, a switch blade secured to the shaft and movable in an arcuate path with the shaft between open and closed positions with respect to the stationary contact, an actuating plunger disposed adjacent to the blade in the open position to engage the blade transversely substantially at the center of percussion, stored energy means disposed adjacent to the plunger to apply a force to the plunger to move the plunger toward the blade, a primary latch disposed to maintain the stored energy means in a stored energy condition, controllable means for actuating the latch to release the stored energy means to actuate the plunger to rotate the blade toward the closed condition, an arcing contact electrically connected to and spaced angularly from the stationary contact with respect to the arcuate path of the blade, the arcing contact being spaced from the arcuate path of the blade and disposed relatively closer to the free end of the blade than the stationary contact when the blade reaches a position in its movement toward the stationary contact in which the arcing contact is substantially in line with the blade.

9. A switch comprising a stationary contact, a rotatable shaft, a switch blade secured to the shaft and movable in an arcuate path with the shaft between open and closed positions with respect to he stationary contact, an actuating plunger disposed adjacent to the blade in the open position to engage the blade transversely substantially at the center of percussion, stored energy means disposed adjacent to the plunger to apply a force to move the plunger toward the blade, a primary latch disposed to maintain the stored energy means in a stored energy condition, controllable means for actuating the latch to release the stored energy means and to actuate the plunger to rotate the blade toward the closed position, and a releasable secondary latch disposed to retain the blade in the open position until the primary latch is actuated to release the stored energy means.

References Cited UNITED STATES PATENTS 1,310,353 7/1919 Kovacs 200-l62 1,956,484 4/1934 Bate 200--162 X 2,621,272 12/1952 Kojis 200l62 X 3,004,116 10/1961 Griscom 200-48 3,004,117 10/1961 Skooglund 20048 ROBERT K. SCHAEFER, Primary Examiner.

H. HOHAUSER, Assistant Examiner. 

5. A SWITCH COMPRISING A STATIONARY CONTACT, A ROTATABLE SHAFT, A SWITCH BLADE MOUNTED ON THE SHAFT AND MOVABLE WITH THE SHAFT IN AN ARCUATE PATH BETWEEN CLOSED AND OPEN POSITION INTO AND OUT OF ENGAGEMENT WITH THE STATIONARY CONTACT, AND RELEASABLE STORED ENERGY MEANS DISPOSED ADJACENT TO THE BLADE FOR APPLYING AN IMPULSE OF FORCE TO THE BLASE TRANSVERSELY SUBSTANTIALLY AT THE CENTER OF PERCUSSION TO ACTUATE THE BLADE TOWARD THE STATIONARY CONTACT, SAID STORED ENERGY MEANS BEING DISENGAGED FROM THE BLADE WHEN THE BLADE IS IN CLOSED POSITION. 